{- youtube-dl integration for git-annex
 -
 - Copyright 2017-2018 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Annex.YoutubeDl (
	youtubeDl,
	youtubeDlTo,
	youtubeDlSupported,
	youtubeDlCheck,
	youtubeDlFileName,
	youtubeDlFileNameHtmlOnly,
) where

import Annex.Common
import qualified Annex
import Annex.Content
import Annex.Url
import Utility.Url (URLString)
import Utility.DiskFree
import Utility.HtmlDetect
import Utility.Process.Transcript
import Logs.Transfer

import Network.URI
import Control.Concurrent.Async

-- youtube-dl is can follow redirects to anywhere, including potentially
-- localhost or a private address. So, it's only allowed to download
-- content if the user has allowed access to all addresses.
youtubeDlAllowed :: Annex Bool
youtubeDlAllowed = httpAddressesUnlimited

youtubeDlNotAllowedMessage :: String
youtubeDlNotAllowedMessage = unwords
	[ "This url is supported by youtube-dl, but"
	, "youtube-dl could potentially access any address, and the"
	, "configuration of annex.security.allowed-http-addresses"
	, "does not allow that. Not using youtube-dl."
	]

-- Runs youtube-dl in a work directory, to download a single media file
-- from the url. Reutrns the path to the media file in the work directory.
--
-- If youtube-dl fails without writing any files to the work directory, 
-- or is not installed, returns Right Nothing.
--
-- The work directory can contain files from a previous run of youtube-dl
-- and it will resume. It should not contain any other files though,
-- and youtube-dl needs to finish up with only one file in the directory
-- so we know which one it downloaded.
--
-- (Note that we can't use --output to specifiy the file to download to,
-- due to <https://github.com/rg3/youtube-dl/issues/14864>)
youtubeDl :: URLString -> FilePath -> Annex (Either String (Maybe FilePath))
youtubeDl url workdir = ifM httpAddressesUnlimited
	( withUrlOptions $ youtubeDl' url workdir
	, return $ Left youtubeDlNotAllowedMessage
	)

youtubeDl' :: URLString -> FilePath -> UrlOptions -> Annex (Either String (Maybe FilePath))
youtubeDl' url workdir uo
	| supportedScheme uo url = ifM (liftIO $ inPath "youtube-dl")
		( runcmd >>= \case
			Right True -> workdirfiles >>= \case
				(f:[]) -> return (Right (Just f))
				[] -> return nofiles
				fs -> return (toomanyfiles fs)
			Right False -> workdirfiles >>= \case
				[] -> return (Right Nothing)
				_ -> return (Left "youtube-dl download is incomplete. Run the command again to resume.")
			Left msg -> return (Left msg)
		, return (Right Nothing)
		)
	| otherwise = return (Right Nothing)
  where
	nofiles = Left "youtube-dl did not put any media in its work directory, perhaps it's been configured to store files somewhere else?"
	toomanyfiles fs = Left $ "youtube-dl downloaded multiple media files; git-annex is only able to deal with one per url: " ++ show fs
	workdirfiles = liftIO $ filterM (doesFileExist) =<< dirContents workdir
	runcmd = youtubeDlMaxSize workdir >>= \case
		Left msg -> return (Left msg)
		Right maxsize -> do
			quiet <- commandProgressDisabled
			opts <- youtubeDlOpts $ dlopts ++ maxsize ++ 
				if quiet then [ Param "--quiet" ] else []
			ok <- liftIO $ boolSystem' "youtube-dl" opts $
				\p -> p { cwd = Just workdir }
			return (Right ok)
	dlopts = 
		[ Param url
		-- To make youtube-dl only download one file when given a
		-- page with a video and a playlist, download only the video.
		, Param "--no-playlist"
		-- And when given a page with only a playlist, download only
		-- the first video on the playlist. (Assumes the video is
		-- somewhat stable, but this is the only way to prevent
		-- youtube-dl from downloading the whole playlist.)
		, Param "--playlist-items", Param "0"
		]

-- To honor annex.diskreserve, ask youtube-dl to not download too
-- large a media file. Factors in other downloads that are in progress,
-- and any files in the workdir that it may have partially downloaded
-- before.
youtubeDlMaxSize :: FilePath -> Annex (Either String [CommandParam])
youtubeDlMaxSize workdir = ifM (Annex.getState Annex.force)
	( return $ Right []
	, liftIO (getDiskFree workdir) >>= \case
		Just have -> do
			inprogress <- sizeOfDownloadsInProgress (const True)
			partial <- liftIO $ sum 
				<$> (mapM getFileSize =<< dirContents workdir)
			reserve <- annexDiskReserve <$> Annex.getGitConfig
			let maxsize = have - reserve - inprogress + partial
			if maxsize > 0
				then return $ Right
					[ Param "--max-filesize"
					, Param (show maxsize)
					]
				else return $ Left $
					needMoreDiskSpace $
						negate maxsize + 1024
		Nothing -> return $ Right []
	)

-- Download a media file to a destination, 
youtubeDlTo :: Key -> URLString -> FilePath -> Annex Bool
youtubeDlTo key url dest = do
	res <- withTmpWorkDir key $ \workdir ->
		youtubeDl url workdir >>= \case
			Right (Just mediafile) -> do
				liftIO $ renameFile mediafile dest
				return (Just True)
			Right Nothing -> return (Just False)
			Left msg -> do
				warning msg
				return Nothing
	return (fromMaybe False res)

-- youtube-dl supports downloading urls that are not html pages,
-- but we don't want to use it for such urls, since they can be downloaded
-- without it. So, this first downloads part of the content and checks 
-- if it's a html page; only then is youtube-dl used.
htmlOnly :: URLString -> a -> Annex a -> Annex a
htmlOnly url fallback a = withUrlOptions $ \uo -> 
	liftIO (downloadPartial url uo htmlPrefixLength) >>= \case
		Just bs | isHtmlBs bs -> a
		_ -> return fallback

-- Check if youtube-dl supports downloading content from an url.
youtubeDlSupported :: URLString -> Annex Bool
youtubeDlSupported url = either (const False) id
	<$> withUrlOptions (youtubeDlCheck' url)

-- Check if youtube-dl can find media in an url.
--
-- While this does not download anything, it checks youtubeDlAllowed
-- for symmetry with youtubeDl; the check should not succeed if the
-- download won't succeed.
youtubeDlCheck :: URLString -> Annex (Either String Bool)
youtubeDlCheck url = ifM youtubeDlAllowed
	( withUrlOptions $ youtubeDlCheck' url
	, return $ Left youtubeDlNotAllowedMessage
	)

youtubeDlCheck' :: URLString -> UrlOptions -> Annex (Either String Bool)
youtubeDlCheck' url uo
	| supportedScheme uo url = catchMsgIO $ htmlOnly url False $ do
		opts <- youtubeDlOpts [ Param url, Param "--simulate" ]
		liftIO $ snd <$> processTranscript "youtube-dl" (toCommand opts) Nothing
	| otherwise = return (Right False)

-- Ask youtube-dl for the filename of media in an url.
--
-- (This is not always identical to the filename it uses when downloading.)
youtubeDlFileName :: URLString -> Annex (Either String FilePath)
youtubeDlFileName url = withUrlOptions go
  where
	go uo
		| supportedScheme uo url = flip catchIO (pure . Left . show) $
			htmlOnly url nomedia (youtubeDlFileNameHtmlOnly' url uo)
		| otherwise = return nomedia
	nomedia = Left "no media in url"

-- Does not check if the url contains htmlOnly; use when that's already
-- been verified.
youtubeDlFileNameHtmlOnly :: URLString -> Annex (Either String FilePath)
youtubeDlFileNameHtmlOnly = withUrlOptions . youtubeDlFileNameHtmlOnly'

youtubeDlFileNameHtmlOnly' :: URLString -> UrlOptions -> Annex (Either String FilePath)
youtubeDlFileNameHtmlOnly' url uo
	| supportedScheme uo url = flip catchIO (pure . Left . show) go
	| otherwise = return nomedia
  where
	go = do
		-- Sometimes youtube-dl will fail with an ugly backtrace
		-- (eg, http://bugs.debian.org/874321)
		-- so catch stderr as well as stdout to avoid the user
		-- seeing it. --no-warnings avoids warning messages that
		-- are output to stdout.
		opts <- youtubeDlOpts
			[ Param url
			, Param "--get-filename"
			, Param "--no-warnings"
			, Param "--no-playlist"
			]
		(Nothing, Just o, Just e, pid) <- liftIO $ createProcess
			(proc "youtube-dl" (toCommand opts))
				{ std_out = CreatePipe
				, std_err = CreatePipe
				}
		output <- liftIO $ fmap fst $ 
			hGetContentsStrict o
				`concurrently`
			hGetContentsStrict e
		ok <- liftIO $ checkSuccessProcess pid
		return $ case (ok, lines output) of
			(True, (f:_)) | not (null f) -> Right f
			_ -> nomedia
	nomedia = Left "no media in url"

youtubeDlOpts :: [CommandParam] -> Annex [CommandParam]
youtubeDlOpts addopts = do
	opts <- map Param . annexYoutubeDlOptions <$> Annex.getGitConfig
	return (opts ++ addopts)

supportedScheme :: UrlOptions -> URLString -> Bool
supportedScheme uo url = case parseURIRelaxed url of
	Nothing -> False
	Just u -> case uriScheme u of
		-- avoid ugly message from youtube-dl about not supporting file:
		"file:" -> False
		-- ftp indexes may look like html pages, and there's no point
		-- involving youtube-dl in a ftp download
		"ftp:" -> False
		_ -> allowedScheme uo u